The present invention relates to methods and apparatus for producing uniform granular compositions, and more particularly to methods and apparatus which may be used for producing of uniform granular detergent compositions.
One of the most widespread ways of manufacturing detergent granules is through a spray drying process. A detergent mixture is sprayed through an atomization nozzle and the resulting droplets are dried in a gas flow in a drying tower. Spraying is usually done through pressure or swirl nozzles. The detergent product obtained by these technologies typically contains particles which widely vary in size. For example, for a swirl atomizer with counterflow drying air, typical particle sizes range from about 100 microns to about 1100 microns, resulting in non-uniform particles or granules.
The difficulty in producing uniform droplets and resulting granules is a well-known problem for conventional atomization technology. Certain atomization methods are known for minimizing this problem. Among them are ultra-sonic, electrostatic, and acoustic atomization techniques. However, none of these techniques are applicable for making detergent granules having a large particle size (i.e. of at least 500 microns). Detergent slurry is typically a highly viscous, non-Newtonian, water-based mixture containing approximately 70% solids. In addition, detergent slurry is typically conductive and corrosive (pH greater than 12). Because of the detergent slurry""s typical high viscosity and high solids content, the slurry cannot be properly processed by conventional ultrasonic atomizers. In addition, the detergent slurry usually cannot be processed by electrostatic atomizers due to the conductivity and viscosity of the detergent slurry. Furthermore, acoustic atomization is typically not possible because the slurry efficiently attenuates the sound waves necessary for such processes.
To meet commercial manufacturing demands, it is typically desired that any atomization method applied to a detergent slurry have a throughput capacity of about 50-60 tons per hour. However, typically atomization technologies are viewed as low-throughput methods and none of the prior known atomization methods are able to process such amounts of slurry in one unit. Accordingly, multiple atomization units would be required to provide the desired throughput capacity. The use of multiple units however requires additional capital expenditures. As such, there remains a need for an efficient process for the preparation of uniform granular compositions, such as detergent compositions, with a relativity high throughput.
Accordingly, it is an object of the present invention to provide novel methods and apparatus for the preparation of uniform granular compositions, which methods and apparatus overcome one or more disadvantages of the prior art. It is a more specific object of the invention to provide methods and apparatus for producing of uniform granular detergent compositions. Another object of the present invention is to provide methods and apparatus having high throughput for the production of uniform granular detergent compositions.
These and additional objects and advantages are provided by methods and apparatus for manufacturing granular compositions according to the invention.
One embodiment of the present invention relates to methods for producing granular compositions. The methods comprise the steps of preparing a viscous liquid mixture, forming a plurality of ligaments from the viscous liquid mixture, cutting the ligaments with one or more liquid jet streams to form pieces, and drying the pieces to form the granular composition.
Another embodiment of the present invention relates to apparatus for producing granular compositions. The apparatus comprise a viscous liquid composition supply, a ligament forming device in fluid communication with the viscous liquid composition supply, one or more liquid jet nozzles adjacent an outlet of the ligament forming device, and a dryer. The methods and apparatus of the present invention are advantageous in providing uniform granular compositions at a relatively high throughput if desired. These and additional objects and advantages will be further apparent in view of the following detailed description.